The shock index (SI) is calculated as the ratio of heart rate to systolic blood pressure and is often used in the assessment of critically ill patients.
A SI > 0.8 has been shown to be an independent predictor of post-intubation hypotension during emergency airway management.
Kristensen and colleagues performed a retrospective review in a single-center in Denmark to evaluate the ability of SI to predict 30-day mortality.
In over 110,000 patients, they found a weaker association of SI with 30-day mortality in patients > 65 years of age, those taking a beta-blocker or calcium channel blocker, or those with a history of hypertension.
Notwithstanding, a SI > 1 was a significant predictor of mortality across all patient populations and should be considered a warning of serious illness.
References
Kristensen AKB, Holler JG, Hallas J, et al. Is shock index a valid predictor of mortality in emergency department patients with hypertension, diabetes, high age, or receipt of beta or calcium channel blockers? Ann Emerg Med 2016; 67:106-13.
